Tyre pressure monitoring systems are in current commercial use in many types of vehicle. These typically involve a tyre valve which contains a sensor adapted to measure tyre pressure and a communication means which allows the sensor value to be received by an appropriate control system within the vehicle. Tyre pressure information is then provided to the driver as and when required—this may be by display on an appropriate user interface, or by warning alerts or system interventions if the tyre pressure reaches an appropriate threshold.
U.S. Pat. No. 6,900,725 describes a tyre pressure monitoring system which may be extended for use with auxiliary tyres beyond those in active use in a main vehicle. Such auxiliary tyres may include a spare tyre for a main vehicle, but also tyres for an auxiliary vehicle such as a trailer. The system described has a learn mode in which auxiliary tyre sensors can be detected and in which the driver (or other user) can provide tyre pressure threshold values.
In practice, it is difficult to use conventional tyre pressure monitoring systems for auxiliary vehicles such as trailers. This is because many alternative forms of auxiliary vehicle could be used, with the result that correct data entry by the driver is relied on to ensure effective pressure monitoring. There are many disadvantages to this. The driver may not have the relevant information readily available, and the need to enter data in this way may affect the driver's ease of use of the relevant vehicle. Moreover, driver error in data entry may lead to significant safety risks. It is desirable to improve tyre monitoring so as to reduce at least some of these disadvantages.